Process for preparing 1,5-diaminonaphthalene derivative

ABSTRACT

In a process where an ortho-alkylnitrobenzene derivative and a vinyl compound as starting materials are used to prepare a 1,5-diaminonaphthalene derivative via a 4-(2-nitrobenzene)propane derivative and a 5-nitro-1-tetralone derivative, the ortho-alkylnitrobenzene derivative and a vinyl compound having an electron withdrawing group such as an acrylonitrile derivative and an acrylate may be reacted in the presence of a base to provide an aromatic nitro compound. An aromatic nitro compound such as 4-(2-nitrobenzene)butanonitrile thus obtained may be cyclized to safely, cost-effectively and selectively provide a 5-nitro-1-tetralone derivative without forming any isomer. Furthermore, from the 5-nitro-1-tetralone derivative, a 1,5-diaminonaphthalene derivative may be prepared without forming any isomer.

This application is a 371 of PCT/JP02/04398 filed May 2, 2002.

TECHNICAL FIELD

The present invention relates to a process for preparing a1,5-diaminonaphthalene derivative. In particular, it relates to aprocess for preparing a 1,5-diaminonaphthalene derivative using a5-nitro-1-tetralone derivative as starting material. A1,5-diaminonaphthalene derivative prepared according to the process ofthis invention is useful as a material for a variety of syntheticresins. For example, a 1,5-diaminonaphthalene derivative may be reactedwith phosgene to form a diisocyanate, which may be then converted into apolyurethane resin, a dicarboxylic acid or its derivative to provide apolyamide resin.

BACKGROUND OF THE INVENTION

Conventionally, a 1,5-diaminonaphthalene derivative has been prepared bynitrating naphthalene to produce a dinitronaphthalene and then reducingthe nitro groups into amino groups. Dinitration of naphthalene, however,produces a 1,8-dinitro derivative in a large amount in addition to thedesired 1,5-dinitro derivative. For example, in nitration of1-nitronaphthalene in a chlorine-containing organic solvent as describedin Japanese Laid-open Patent Publication No. 51-070757,1,5-dinitronaphthalene is produced in an yield of 30% while1,8-dinitronaphthalene in an yield of 65%. That is, the 1,8-dinitroderivative is formed in a two-fold or more amount of the 1,5-dinitroderivative. 1,8-Dinitronaphthalene may be readily reduced into1,8-diaminonaphthalene, which may be, for example, used as a materialfor a dye. However, when a demand for 1,8-diaminonaphthalene is reduced,production of 1,5-dinitronaphthalene is reduced, making1,5-diaminonaphthalene less available.

In the light of such status, there have been attempts for increasing anyield of the 1,5-derivative in nitration of naphthalene. For example, WO99-12887 has described that using Nafion® as an acid, 1-nitronaphthaleneis nitrated with nitric acid to give 1,5- and 1,8-dinitronaphthalenes inyields of 34.1% and 38.0%, respectively. Thus, the proportion of the1,5-dinitro derivative may be improved, but the 1,8-derivative is stillformed in a large amount.

As described above, the current preparation procedure produces the1,8-dinitro derivative in a large amount in addition to the 1,5-dinitroderivative. Thus, there has been needed to provide a process forselectively producing a 1,5-diaminonaphthalene derivative withoutforming isomers.

Besides the process involving dinitration of naphthalene and reductionof the nitro groups, many alternative processes have been suggested; forexample, amination of 1,5-dihydroxynaphthalene as a starting material(U.S. Pat. No. 5,113,025, Japanese Laid-open Patent Publication No.59-29061), amination of a 5-halogeno-1-aminonaphthalene or1,5-dihalogenonaphthalene (Japanese Laid-open Patent Publication No.7-278066, U.S. Pat. No. 3,787,496) and amination of sodium1,5-naphthalenedisulfonate (Nihon Kagakukai Shi, 522 (1974)). However, acumene process for preparing 1,5-dihydroxynaphthalene tends to causerearrangement of a isopropyl group in 1,5-diisopropylnaphthalene as astarting material to the β-position due to steric hindrance, leading toformation of isomers as is in the process involving dinitration andreduction. It is, therefore, not a selective method. Halogenation orsulfonation of naphthalene is also less selective.

SUMMARY OF THE INVENTION

We have intensely investigated for providing a process for selectivelypreparing a 1,5-diaminonaphthalene derivative without forming isomers,and have found a process for preparing a 1,5-diaminonaphthalenederivative using a 5-nitro-1-tetralone derivative as an intermediate,achieving this invention.

Specifically, this invention comprises the embodiments described in thefollowing [1] to [7].

[1] A process for preparing a 1,5-diaminonaphthalene derivativecomprising:

(i) the first step comprising reacting an ortho-alkylnitrobenzenerepresented by formula (1):

wherein R¹ to R⁴, which may be the same or different, representhydrogen, alkyl having 1 to 4 carbon atoms, aromatic hydrocarbon having6 to 12 carbon atoms, or halogen; and R⁵ represents hydrogen, with avinyl compound represented by formula (2):

wherein R⁶ and R⁷, which may be the same or different, representhydrogen, alkyl having 1 to 4 carbon atoms, or halogen; and X representsan electron withdrawing group, provided that R⁶ and R⁷ are mutually cis-or trans-configured, in the presence of a base, to produce an aromaticnitro compound represented by formula (3):

wherein R¹ to R⁷ are as defined in formulas (1) and (2); and Xrepresents an electron withdrawing group, which may be the same as ordifferent from X as defined in formula (2);

(ii) the second step of cyclizing the aromatic nitro compoundrepresented by formula (3) to produce a 5-nitro-1-tetralone derivativerepresented by formula (4):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2);and

(iii) the third step comprising reacting the 5-nitro-1-tetralonederivative represented by formula (4) with an amine to provide anintermediate, which is then reduced and aromatized to produce the1,5-diaminonaphthalene derivative represented by formula (5):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2).

[2] The process as described in [1], wherein X in formula (2) is oneselected from the group consisting of CN and CO₂R⁸ where R⁸ representsalkyl having 1 to 7 carbon atoms, cycloalkyl, aromatic hydrocarbonhaving 6 to 12 carbon atoms or aralkyl.

[3] The process as described in [1], wherein X in formula (3) is oneselected from the group consisting of CONH₂, CN, CO₂H and CO₂R⁸ where R⁸represents alkyl having 1 to 7 carbon atoms, cycloalkyl, aromatichydrocarbon having 6 to 12 carbon atoms or aralkyl.

[4] The process as described in [1] or [2], wherein the reaction of theortho-alkylnitrobenzene represented by formula (1) with the vinylcompound represented by formula (2) in the first step is conducted inthe presence of at least one selected from the group consisting of asolvent capable of dissolving at least part of the base and a catalystcapable of solubilizing the base.

[5] The process as described in [4], wherein the solvent capable ofdissolving at least part of the base is a circular urea derivative.

[6] The process as described in any of [1] to [5], wherein in the thirdstep, a hydroxylamine derivative as the amine is reacted with the5-nitro-1-tetralone derivative represented by formula (4) or an ammoniaderivative as the amine is reacted with the 5-nitro-1-tetralonederivative represented by formula (4) in the presence of hydrogenperoxide, to provide an oxime represented by formula (6):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2),which is then converted by aromatization into a5-nitro-1-aminonaphthalene derivative represented by formula (7):

wherein R¹ to R⁴ and R⁶ to R⁷ arc as defined in formulas (1) and (2),which is then reduced into the 1,5-diaminonaphthalene derivativerepresented by formula (5).

[7] The process as described in any of [1] to [5], wherein in the thirdstep, an ammonia derivative as the amine is reacted with the5-nitro-1-tetralone derivative represented by formula (4) to provide animine represented by formula (8):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2),which is then reduced and aromatized to provide the1,5-diaminonaphthalene derivative represented by formula (5).

The above process wherein an ortho-alkylnitrobenzene derivative and avinyl compound are used as starting materials to give a5-nitro-1-tetralone derivative, from which a corresponding1,5-diaminonaphthalene derivative is prepared, allows the1,5-diaminonaphthalene derivative to be selectively prepared withoutforming isomers.

DETAILED DESCRIPTION OF THE INVENTION

First, there will be described the first step in the process accordingto this invention, in which an ortho-alkylnitrobenzene derivative isreacted with a vinyl compound to prepare an aromatic nitro compound.

In the present invention, in formula (1), R¹ to R⁴ may be the same ordifferent, and represent hydrogen, alkyl having 1 to 4 carbon atoms,aromatic hydrocarbon having 6 to 12 carbon atoms or halogen; and R⁵represents hydrogen.

In the present invention, in formula (2), R⁶ and R⁷ may be the same ordifferent, and represent hydrogen, alkyl having 1 to 4 carbon atoms orhalogen; X represents an electron withdrawing group; and R⁶ and R⁷ aremutually cis- or trans-configured.

Examples of alkyl in R¹ to R⁴ and R⁶ and R⁷ include methyl, ethyl,n-propyl, isopropyl, n-butyl, i-butyl and t-butyl.

Examples of aromatic hydrocarbon in R¹ to R⁴ include phenyl, tolyl andxylyl.

Examples of halogen in R¹ to R⁴ and R⁶ and R⁷ include fluorine,chlorine, bromine and iodine.

In formula (2), R⁸ when X is CO₂R⁸ represents alkyl having 1 to 7 carbonatoms, cycloalkyl, aromatic hydrocarbon having 6 to 12 carbon atoms, oraralkyl. Examples of alkyl having 1 to 7 carbon atoms include methyl,ethyl, n-propyl, isopropyl, n-butyl, i-butyl, t-butyl, n-pentyl andn-hexyl. Examples of cycloalkyl include cyclopentyl and cyclohexyl.Example of aromatic hydrocarbon include phenyl, tolyl and xylyl.Examples of aralkyl is benzyl and phenethyl.

In the present invention, examples of an ortho-alkylnitrobenzenederivative represented by formula (1) include 2-methylnitrobenzene,2-methyl-6-isopropylnitrobenzene, 2-methyl-5-t-butylnitrobenzene,2,4-dimethylnitrobenzene, 2-methyl-4-chloronitrobenzene,2-ethylnitrobenzene and 2-benzylnitrobenzene.

In the present invention, examples of an electron withdrawing group X ina vinyl compound represented by formula (2) is preferably one selectedfrom the group consisting of CN and CO₂R⁸ where R⁸ represents alkylhaving 1 to 7 carbon atoms, cycloalkyl, aromatic hydrocarbon having 6 to12 carbon atoms or aralkyl. Examples of an acrylonitrile derivative inwhich X is CN include acrylonitrile, methacrylonitrile, crotononitrile,2-chloroacrylonitrile, 3-chloroacrylonitrile and 3-ethylacrylonitrile.Examples of an acrylate in which X is CO₂R⁸ include methyl acrylate,ethyl acrylate, isopropyl acrylate, t-butyl acrylate, methylmethacrylate, methyl crotonate, methyl 2-chloroacrylate, methyl3-chloroacrylate and isopropyl 3-chloroacrylate.

Examples of a nitrobenzenenitrile derivative represented by formula (3),in which X is nitrile, include 4-(2-nitrobenzene)butanonitrile,4-(2-nitrobenzene)-2-methylbutanonitrile,4-(2-nitrobenzene)-3-methylbutanonitrile,4-(2-nitrobenzene)-3-ethylbutanonitrile,4-(2-nitrobenzene)-3-chlorobutanonitrile,4-(2-nitrobenzene)-n-heptanonitrile,4-(2-nitro-3-isopropylbenzene)butanonitrile,4-(2-nitro-3-butylbenzene)butanonitrile,4-(2-nitro-4-t-butylbenzene)butanonitrile,4-(2-nitro-5-methylbenzene)butanonitrile and4-(2-nitro-3-methylbenzene)-2-methylbutanonitrile. In particular,4-(2-nitrobenzene)butanonitrile is preferable because it can beconverted into a 5-nitro-1-tetralone which used in a variety ofapplications.

Examples of a nitrobenzenecarboxylic acid represented by formula (3)where X is carboxyl, include 4-(2-nitrobenzene)butyric acid,4-(2-nitrobenzene)-2-methylbutyric acid,4-(2-nitrobenzene)-3-methylbutyric acid,4-(2-nitrobenzene)-3-ethylbutyric acid,4-(2-nitrobenzene)-3-chlorobutyric acid,4-(2-nitro-3-isopropylbenzene)butyric acid,4-(2-nitro-3-butylbenzene)butyric acid,4-(2-nitro-4-t-butylbenzene)butyric acid,4-(2-nitro-5-methylbenzene)butyric acid,4-(2-nitro-5-methylbenzene)butyric acid and4-(2-nitro-3-methylbenzene)-2-methylbutyric acid. In particular,4-(2-nitrobenzene)butyric acid is preferable because it can be convertedinto a 5-nitro-1-tetralone which is used in a variety of applications.

Examples of a nitrobenzenecarboxylate represented by formula (3) where Xis CO₂R⁸ include methyl 4-(2-nitrobenzene)butyrate, methyl4-(2-nitrobenzene)-2-methylbutyrate, methyl4-(2-nitrobenzene)-3-methylbutyrate, methyl4-(2-nitrobenzene)-3-ethylbutyrate, methyl4-(2-nitrobenzene)-3-chlorobutyrate, methyl4-(2-nitro-3-isopropylbenzene) butyrate, methyl4-(2-nitro-3-butylbenzene) butyrate, methyl 4-(2-nitro-4-t-butylbenzene)butyrate, methyl 4-(2-nitro-5-methylbenzene) butyrate, methyl4-(2-nitro-3-methylbenzene)-2-methylbutyrate, ethyl4-(2-nitrobenzene)butyrate, ethyl 4-(2-nitrobenzene)-2-methylbutyrate,ethyl 4-(2-nitrobenzene)-3-methylbutyrate, ethyl4-(2-nitrobenzene)-3-ethylbutyrate, ethyl4-(2-nitrobenzene)-3-chlorobutyrate, ethyl4-(2-nitro-3-isopropylbenzene) butyrate, ethyl4-(2-nitro-3-butylbenzene) butyrate, ethyl 4-(2-nitro-4-t-butylbenzene)butyrate, ethyl 4-(2-nitro-5-methylbenzene) butyrate, ethyl4-(2-nitro-3-methylbenzene)-2-methylbutyrate, cyclohexyl4-(2-nitrobenzene)butyrate, phenyl 4-(2-nitrobenzene)butyrate and benzyl4-(2-nitrobenzene)butyrate. In particular, methyl and ethyl4-(2-Nitrobenzene)butyrate are preferable because they can be readilyconverted into a 5-nitro-1-tetralone which is used in a variety ofapplications.

Examples of a nitrobenzenecarboxamide represented by formula (3) where Xis CONH₂, include 4-(2-nitrobenzene)butyramide,4-(2-nitrobenzene)-2-methyl butyramide,4-(2-nitrobenzene)-3-methylbutyramide, 4-(2-nitrobenzene)-3-ethylbutyramide, 4-(2-nitrobenzene)-3-chlorobutyramide,4-(2-nitrobenzene)-heptyramide,4-(2-nitro-3-isopropylbenzene)butyramide,4-(2-nitro-3-butylbenzene)butyramide,4-(2-nitro-4-t-butylbenzene)butyramide,4-(2-nitro-5-methylbenzene)butyramide,4-(2-nitro-5-methylbenzene)butyramide,4-(2-nitro-3-methylbenzene)-2-methylbutyramide and4-(2-nitro-5-methylbenzene)-valeramide. In particular,4-(2-nitrobenzene)butyramide is preferable because it can be convertedinto a 5-nitro-1-tetralone, which is used in a variety of applications.

The compounds represented by formulas (1) to (3) are not limited tothose described above.

A nitrobenenecarboxamide represented by formula (3) where X is CONH₂ canbe prepared by reacting a nitrobenzenenitrile derivative represented byformula (3) where X is nitrile with water under acidic conditions. Anacid used for reaction of the nitrobenzenenitrile derivative with waterunder acidic conditions may be any acid by which the nitrile group canbe protonated; for example, sulfuric acid and sulfonic acids such asp-toluenesulfonic acid, chlorosulfonic acid, trifluoromethanesulfonicacid. Sulfuric acid is preferable because it is inexpensive and readilyavailable. The amount of the acid used must be one or more equivalent tothe nitrobenzenenitrile derivative. The reaction is initiated bycontacting the nitrobenzenenitrile derivative with the acid underanhydrous conditions. A contact temperature and a contact period mayvary depending on the type and the amount of the acid. For example, whenusing 20 equivalents of sulfuric acid, the reaction can be substantiallycompleted by treatment at 100° C. for 4 hours. In the reaction, asolvent may be used, which must be inert during the reaction. A reactionpressure may be an ambient, increased or reduced pressure as long as aproper reaction temperature can be maintained.

Then, the mixture of the acid and the nitrobenzenenitrile derivative canbe reacted with water to provide a nitrobenzenecarboxamide. The amountof water used must be one or more equivalent to the nitrobenzenenitrilederivative. A reaction temperature may vary depending on the type of theacid, but a lower temperature is generally advantageous. If the reactionis conducted at an elevated temperature, the nitrobenzenecarboxamide maybe further hydrolyzed into a corresponding nitrobenzenecarboxylic acid.A reaction temperature is 50 to 200° C., preferably 50 to 150° C. Areaction period may be quite short; specifically, 5 min or less issufficient. A longer reaction period may lead to hydrolysis to thenitrobenzenecarboxylic acid as is at a higher reaction temperature. Asdescribed above, a reaction temperature and a reaction period must becarefully chosen. Herein, water containing a basic compound may be used.Specifically, water containing a basic compound may be added, oralternatively a basic compound or water containing a basic compound maybe added after adding water. By adding a basic compound, a higherreaction temperature and a longer reaction period may be employed whilepreventing hydrolysis into a nitrobenzenecarboxylic acid derivative.

A nitrobenzenecarboxamide may be obtained as crystals after reactingwith water when it has a higher melting point or is highlycrystallizable. The crystals may be washed with water for removing theacid, salts and/or the basic compound. If necessary, the crystals arepurified by, for example, recrystallization. When a melting point is toolow to give crystals after reaction with water, the product may beextracted, concentrated as usual, and then isolated by, for example,distillation or recrystallization. These treatments or reactions arepreferably conducted in a liquid phase, and may be conducted batchwiseor in a continuous system.

Alternatively, a nitrobenzenecarboxamide may be prepared by reacting anitrobenzene carboxylic acid represented by formula (3) where X iscarboxyl and/or its derivative (an ester or acid halide), with ammonia.

When directly reacting the nitrobenzenecarboxylic acid with ammonia, acompound which can act as a dehydrating agent or a condensing agent suchas DCC may be used. In the reaction without a condensing agent, thesystem must be heated. The reaction may be conducted either in a liquidor a gaseous phase, but a liquid phase is preferable in the light of avolumetric efficiency. Although the reaction may be conducted without asolvent, ammonia liquefied in an autoclave may be used as a solvent oralternatively a solvent inert to the reaction may be added. A reactiontemperature and a reaction period may vary depending on the type of adehydrating agent or condensing agent used. A reaction pressure ispreferably an ambient pressure or higher.

When reacting an ester of a nitrobenzenecarboxylic acid with ammonia, acatalyst may be added. Without a catalyst, the reaction system must beheated. The reaction may be conducted either in a liquid phase or in agaseous phase, but a liquid phase is preferable in the light of avolmetric efficiency. Although the reaction may be conducted without asolvent, ammonia liquefied in an autoclave may be used as a solvent oralternatively a solvent inert to the reaction may be added. A reactiontemperature and a reaction period may vary depending on the type of acatalyst used. A reaction pressure is preferably an ambient pressure orhigher.

When reacting an acid halide of a nitrobenzenecarboxylic acid withammonia, a catalyst may be added, a desalting agent may be added, or anexcessive ammonia may be added as a desalting agent. The reaction may beconducted either in a liquid phase or in a gaseous phase, but a liquidphase is preferable in the light of a volmetric efficiency. Although thereaction may be conducted without a solvent, ammonia liquefied in anautoclave may be used as a solvent or alternatively a solvent inert tothe reaction may be added. A reaction temperature and a reaction periodmay vary depending on the type of a catalyst or desalting agent used. Areaction pressure is preferably an ambient pressure or higher.

These reactions may be conducted batchwise or in a continuous system.

The reaction of the compounds represented by formulas (1) and (2) in thefirst step in the process according to the present invention isconducted in the presence of a base, preferably a strong base. Examplesof such a strong base include solid bases such as NaOH, KOH, LiOH,Na₂CO₃, K₂CO₃, CH₃ONa, t-BuOK, NaH, C₆H₅ONa, (CH₃)₄N⁺OH−, (Bu)₄N⁺OH−,DBU and basic ion-exchange resins, particularly preferably NaOH and KOH.

Examples of a solvent capable of dissolving at least part of a base usedinclude circular urea derivatives such as1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidinone,1,3-dipropyl-2-imidazolidinone and 1,3-dibutyl-2-imidazolidinone; amidessuch as formamide, N-methylformamide, N,N-dimethylformamide,N-methylacetamide, N,N-dimethylacetamide and hexamethylphosphoramide;dimethylsulfoxide; sulfolane; pyridine; morpholine; ethers such astetrahydrofuran and 1,4-dioxane; nitrites such as acetonitrile andpropionitrile; and lower alcohols such as methanol, ethanol andisopropanol. These solvents may be mixed with water or used incombination of two or more for improving a solubility of a base. Whenusing a catalyst capable of solubilizing a base, any solvent which isinert to the reaction may be used. An example of a preferable solvent isa mixture of 1,3-dimethyl-2-imidazolidinone and water.

An example of a catalyst capable of solubilizing a base is a phasetransfer catalyst. Examples of a phase transfer catalyst includecetyltrimethylammonium bromide, tetrabutylammonium chloride,tetrabutylammonium bromide and tetrabutylammonium hydroxide.

When reacting the compounds represented by formulas (1) and (2) as thestarting materials in the presence of a base in the first step of theprocess according to the present invention, a molar ratio of thestarting materials is preferably base/ortho-alkylnitrobenzenederivative/acrylonitrile derivative=0.01 to 1.0/1/0.1 to 5 forpreparation of a nitrobenzenenitrile derivative represented by formula(2) where X is nitrile; and base/ortho-alkylnitrobenzenederivative/acrylate=0.01 to 1.0/1/0.1 to 10 for preparation of anitrobenzenecarboxylate represented by formula (2) where X is CO₂R⁸.

When reacting the compounds represented by formulas (1) and (2) as thestarting materials in the presence of a base in the first step of theprocess according to the present invention, the amount of a solventcapable of dissolving at least part of a base is 0.1 to 20 weight parts,preferably 0.5 to 20 weight parts to one part of anortho-alkylnitrobenzene derivative, and the amount of a catalyst capableof solubilizing a base is 0.1 to 10 mole % to theortho-alkylnitrobenzene derivative.

When reacting the compounds represented by formulas (1) and (2) as thestarting materials in the presence of a base in the first step of theprocess according to the present invention, a reaction temperature mayvary depending on a base and a solvent used, but is preferably 150° C.or lower because the reaction must be conducted at a temperature equalto or lower than a decomposition temperature of anortho-alkylnitrobenzene derivative. A reaction period may be generally 1min to 6 hours.

When reacting the compounds represented by formulas (1) and (2) as thestarting materials in the presence of a base in the first step of theprocess according to the present invention, a reaction pressure may bean ambient, increased or reduced pressure as long as the startingmaterials or the solvent may not be removed from the system, and may begenerally an ambient pressure.

The reaction is preferably conducted in an atmosphere of an inert gassuch as nitrogen or under oxygen-free conditions.

When an acrylate represented by formula (2) where X is CO₂R⁸ is used asa starting material and a solvent is mixed with water, a reactionproduct contains a nitrobenzenecarboxylic acid derivative.

The reaction may be conducted batchwise or in a continuous system. Thereaction may be quenched by pouring the reaction mixture into ice-water,and then the mixture is neutralized to pH 6 to 7 with an acid. Afterseparating phases using an organic solvent, the organic solvent may beremoved to provide a viscous liquid containing the desired aromaticnitro compound represented by formula (3).

Examples of an extraction solvent used include isopropyl ether, ethylacetate, butyl acetate, carbon disulfide, carbon tetrachloride, hexane,cyclohexane, petroleum ether, toluene, xylenes, chloroform,dichloromethane, 1,2-dichloroethane, trichloroethylene,1,2-dichlorobenzene, chlorobenzene, benzonitrile, nitromethane,nitrobenzene, anisole and diethyleneglycol dimethyl ether. Any solventother than those described above may be used as long as it can dissolvethe desired compound, can be separated from water, is stable under thephase separation process and has physical properties such as a boilingpoint within a preferable range.

Column chromatography or distillation at a reduced pressure of theviscous liquid thus obtained may provide a pure nitrobenzenenitrilederivative, nitrobenzenecarboxylic acid, nitrobenzenecarboxylate ornitrobenzenecarboxamide. When a mixture of a nitrobenzenecarboxylic acidand a nitrobenzenecarboxylate is obtained, each compound may beseparately collected by column chromatography or distillation, oralternatively the mixture may be esterified or hydrolyzed to convert thecarboxylic acid into the ester or the ester into the carboxylic acidbefore the collection.

These compounds may be collected and purified by recrystallization orcolumn chromatography when they have a high melting point or are easilycrystallized, or by distillation at a reduced pressure or columnchromatography when they have a low melting point or are poorlycrystallized and exhibit good thermal stability.

Examples of an aromatic nitro compound represented by formula (3)include 4-(2-nitrobenzene)butanonitrile,4-(2-nitrobenzene)-2-methylbutanonitrile,4-(2-nitrobenzene)-3-methylbutanonitrile,4-(2-nitrobenzene)-3-ethylbutanonitrile,4-(2-nitrobenzene)-3-chlorobutanonitrile,4-(2-nitro-3-isopropylbenzene)butanonitrile,4-(2-nitro-3-butylbenzene)butanonitrile,4-(2-nitro-4-t-butylbenzene)butanonitrile,4-(2-nitro-5-methylbenzene)butanonitrile,4-(2-nitro-3-methylbenzene)-2-methylbutanonitrile,4-(2-nitro-5-isopropylbenzene)butanonitrile,4-(2-nitro-5-chlorobenzene)butanonitrile, 4-(2-nitrobenzene)butyricacid, 4-(2-nitrobenzene)-2-methylbutyric acid,4-(2-nitrobenzene)-3-methylbutyric acid,4-(2-nitrobenzene)-3-ethylbutyric acid,4-(2-nitro-5-isopropylbenzene)butyric acid,4-(2-nitro-5-chlorobenzene)butyric acid,4-(2-nitrobenzene)-3-chlorobutyric acid,4-(2-nitro-3-isopropylbenzene)butyric acid,4-(2-nitro-3-butylbenzene)butyric acid,4-(2-nitro-4-t-butylbenzene)butyric acid,4-(2-nitro-5-methylbenzene)butyric acid,4-(2-nitro-3-methylbenzene)-2-methylbutyric acid, methyl4-(2-nitrobenzene)butyrate, methyl 4-(2-nitrobenzene)-2-methylbutyrate,methyl 4-(2-nitrobenzene)-3-methylbutyrate, methyl4-(2-nitrobenzene)-3-ethylbutyrate, methyl4-(2-nitrobenzene)-3-chlorobutyrate, methyl4-(2-nitro-3-isopropylbenzene)butyrate, methyl4-(2-nitro-3-butylbenzene)butyrate, methyl4-(2-nitro-4-t-butylbenzene)butyrate, methyl4-(2-nitro-5-methylbenzene)butyrate, methyl4-(2-nitro-3-methylbenzene)-2-methylbutyrate, methyl4-(2-nitro-5-isopropylbenzene)butyrate, methyl4-(2-nitro-5-chlorobenzene)butyrate, ethyl 4-(2-nitrobenzene)butyrate,ethyl 4-(2-nitrobenzene)-2-methylbutyrate, ethyl4-(2-nitrobenzene)-3-methylbutyrate, ethyl4-(2-nitrobenzene)-3-ethylbutyrate, ethyl4-(2-nitrobenzene)-3-chlorobutyrate, ethyl 4-(2-nitrobenzene)butyrate,ethyl 4-(2-nitro-3-isopropylbenzene)butyrate, ethyl4-(2-nitro-3-butylbenzene)butyrate, ethyl4-(2-nitro-4-t-butylbenzene)butyrate, ethyl4-(2-nitro-5-methylbenzene)butyrate, ethyl4-(2-nitro-3-methylbenzene)-2-methylbutyrate, ethyl4-(2-nitro-5-isopropylbenzene)butyrate, ethyl4-(2-nitro-5-chlorobenzene)butyrate, cyclohexyl4-(2-nitrobenzene)butyrate, phenyl 4-(2-nitrobenzene)butyrate, benzyl4-(2-nitrobenzene)butyrate, 4-(2-nitrobenzene)butyramide,4-(2-nitrobenzene)-2-methylbutyramide,4-(2-nitrobenzene)-3-methylbutyramide,4-(2-nitrobenzene)-3-ethylbutyramide,4-(2-nitro-5-isopropylbenzene)butyramide,4-(2-nitro-5-chlorobenzene)butyramide,4-(2-nitrobenzene)-3-chlorobutyramide,4-(2-nitro-3-isopropylbenzene)butyramide,4-(2-nitro-3-butylbenzene)butyramide,4-(2-nitro-4-t-butylbenzene)butyramide,4-(2-nitro-5-methylbenzene)butyramide and4-(2-nitro-3-methylbenzene)-2-methylbutyramide. In particular,4-(2-nitrobenzene)butanonitrile, 4-(2-nitrobenzene)butyric acid, methyl4-(2-nitrobenzene)butyrate, ethyl 4-(2-nitrobenzene)butyrate and4-(2-nitrobenzene)butyramide are preferable because they may be readilyconverted into a 5-nitro-1-tetralone which is used in a variety ofapplications.

There will be described the cyclization in the second step in theprocess according to the present invention.

The cyclization of an aromatic nitro compound represented by formula (3)into a 5-nitro-1-tetralone derivative represented by formula (4) isusually conducted using an acid catalyst. Examples of such an acidinclude strong acids such as sulfuric acid and polyphosphoric acid;superacids such as oleum, chlorosulfonic acid, trifluoromethanesulfonicacid and fluorosulfonic acid; and Lewis-acid-containing superacids suchas fluorosulfonic acid or chlorosulfonic acid containing a small amountof, e. g., SO₃ or SbF₅. Solid superacids such as sulfated zirconia andsulfated tin oxide may be also used. The amount of the acid is one ormore equivalent to the substrate represented by formula (3). Thecyclization may be conducted in such an acid or in a solvent inert tothe acid.

A reaction temperature is generally 20° C. to 200° C., preferably 50 to150° C. A reaction period is generally 5 min to 15 hours, preferably 20min to 10 hours.

A reaction pressure may be an ambient or increased pressure or, if theappropriate reaction temperature can be maintained, a reduced pressure.

The reaction may be conducted batchwise or in a continuous system.

Water is added to a reaction mixture. Phases are separated using anorganic solvent. After washing the organic layer with water, the organicsolvent is removed to give a crude 5-nitro-1-tetralone derivative. Theacid may be recovered by distillation before adding water. The recoveredacid by distillation may be reused in the cyclization. When an excessivesuperacid is used, the superacid is preferably removed from the reactionmixture by, for example, distillation before adding water. Sinceaddition of water to a strong acid may be an exothermic process, wateris preferably added with cooling. The acid used is diluted or decomposedwith water or methanol generated together with a tetralone derivativefrom the cyclization (hereinafter, such a diluted or decomposed acid isreferred to as a “waste acid”). For example, when using fluorosulfonicacid in the reaction, it is decomposed with water or methanol to formHF, sulfuric acid and so on. The waste acid thus generated may be usedto neutralize a base used in the reaction between the compoundsrepresented by formulas (1) and (2).

Examples of an organic solvent used herein include isopropyl ether,ethyl acetate, butyl acetate, carbon disulfide, carbon tetrachloride,hexane, cyclohexane, petroleum ether, toluene, xylenes, chloroform,dichloromethane, 1,2-dichloroethane, trichloroethylene,o-dichlorobenzene, chlorobenzene, benzonitrile, nitromethane,nitrobenzene, anisole and diethyleneglycol dimethyl ether, particularlypreferably isopropyl ether, ethyl acetate and butyl acetate. Any solventother than those described above may be used as long as it can dissolvethe desired compound, can be separated from water, is stable under thephase separation process and has physical properties such as a boilingpoint within a preferable range.

When an aromatic nitro compound represented by formula (3) is anitrobenzenecarboxamide, the cyclization for forming a5-nitro-1-tetralone derivative represented by formula (4) may beconducted by contacting the material with a dehydrating agent. Thedehydrating agent may be preferably acidic; for example, polyphosphoricacid and phosphorous oxides. These dehydrating agents may be used aloneor in combination with the strong acid described above. A reactiontemperature and a reaction period may vary depending on the types of theacid and the dehydrating agent, but it must be 200° C. or lower becausean excessively elevated temperature may cause decomposition of areaction product. A reaction pressure may be an ambient, increased orreduced pressure as long as an appropriate reaction temperature may bemaintained. A reaction solvent, if used, is preferably inert in thereaction and contains a minimum amount of water. The reaction ispreferably conducted in a liquid phase and may be conducted batchwise orin a continuous system.

The crude 5-nitro-1-tetralone derivative may be purified byrecrystallization when it has a high melting point or is readilycrystallized, or by distillation when it has a low melting point or isless crystallizable.

Examples of a 5-nitro-1-tetralone derivative represented by formula (4)include 5-nitro-1-tetralone, 5-nitro-2-methyl-1-tetralone,5-nitro-3-methyl-1-tetralone, 5-nitro-3-ethyl-1-tetralone,5-nitro-3-chloro-1-tetralone, 5-nitro-4-n-propyl-1-tetralone,5-nitro-6-isopropyl-1-tetralone, 5-nitro-6-n-butyl-1-tetralone,5-nitro-7-t-butyl-1-tetralone, 5-nitro-8-methyl-1-tetralone,5-nitro-8-chloro-1-tetralone, 5-nitro-2,6-dimethyl-1-tetralone,5-nitro-4,8-dimethyl-1-tetralone and 5-nitro-8-isopropyl-1-tetralone. Inparticular, 5-nitro-1-tetralone is preferable because it may beconverted into 1,5-diaminonaphthalene.

There will be described a conversion into a 1,5-diaminonaphthalenederivative in the third step in the process according to this invention.

A 5-nitro-1-tetralone derivative represented by formula (4) may be thenconverted into a desired 1,5-diaminonaphthalene derivative by 1) oximeformation, conversion into a 5-nitro-1-aminonaphthalene derivative, andthen reduction of the nitro groups, or 2) imine formation, aromatizationand then reduction of the nitro groups.

A 5-nitro-1-tetralone derivative may be converted into an oxime by acommon oxime-formation process. An oxime-forming agent may behydroxylamine or a salt of hydroxylamine. Examples of a salt ofhydroxylamine include hydroxylamine hydrochloride and hydroxylaminesulfate. Hydroxylamine may be obtained by neutralizing such a salt witha basic compound or by reacting ammonia with a peroxide such as hydrogenperoxide. Hydroxylamine may be isolated by an appropriate method such asdistillation, and may be used after extraction, or directly used as itis.

A reaction solvent in the oxime formation may be any solvent which isinert in the reaction. Examples of such a solvent include alcohols andalcohols containing an acidic compound such as acetic acid.

A reaction temperature is from 20° C. to a temperature at whichhydroxylamine or its salt decomposes. It is generally 20 to 150° C.,preferably 50 to 120° C.

A reaction pressure may be an ambient pressure, but an increased orreduced pressure may be employed as long as an appropriate reactiontemperature may be maintained.

A reaction period is 1 min or longer. A product may be isolated by anappropriate method such as distillation, recrystallization,reprecipitation and column chromatography, or some of the reactionsolvent may be evaporated. Alternatively, when the reaction solvent isinert in the next step, the reaction mixture may be directly usedwithout further concentration or isolation.

Conversion of the oxime into a 5-nitro-1-aminonaphthalene derivative maybe conducted using a reagent capable of cleaving the N—O bond in theoxime group (═NOH) in a dehydration reaction. For example, the oxime maybe heated in acetic acid as a solvent in the presence of hydrochloricacid to provide a desired 5-nitro-1-aminonaphthalene hydrochloride. Areaction temperature and a reaction period may vary depending on areagent used, and may be chosen such that the N—O bond in the oximegroup can be cleaved in a dehydration reaction as described above. Areaction temperature is generally 50 to 250° C., preferably 50 to 200°C. For facilitating elimination of OH, the OH in the oxime group may beconverted into a functional group which may be readily eliminated, forexample, into OCOCH₃ using acetic anhydride. A reaction pressure may bean ambient or increased pressure. When the dehydrating reagent isgaseous, it may be fed at an ambient pressure, but it is advantageouslycharged in a closed system at an increased pressure.

After the oxime formation, conversion into a 5-nitro-1-aminonaphthalenederivative is conducted, which may be a one-step reaction.

The nitro group may be converted into an amino group by directly using amethod for converting a nitrobenzene derivative into an anilinederivative, but reduction with hydrogen using a hydrogenation catalystis the most cost-effective process. Examples of a hydrogenation catalystinclude Raney metals such as Raney Ni and Raney Co; and platinum-groupcatalysts such as Pd/C and Pt/alumina. The reaction may be conducted ina gaseous or liquid phase. A solvent used in a liquid phase reaction maybe any inert solvent in the reaction, preferably alcohols and amides. Areaction temperature is generally an ambient temperature to 150° C.,preferably 50 to 100° C. A reaction pressure may be an ambient pressureor higher, but an excessively higher hydrogen pressure may causehydrogenation on the naphthalene ring.

All the reactions of oxime formation, conversion into anaminonaphthalene derivative and reduction of a nitro group may beconducted batchwise or in a continuous system.

Alternatively, a 5-nitro-1-tetralone derivative may be converted into a1,5-diaminonaphthalene derivative via an imine instead of an oxime.

A 5-nitro-1-tetralone derivative may be converted into an imine byreacting the nitro compound with an excessive amount of ammonia and/oran ammonium salt. In the reaction, a dehydrating agent may be added. Thereaction may be conducted at an ambient or increased pressure, but whenusing ammonia, the reaction is preferably conducted at an increasedpressure.

Aromatization of the tetralin ring and reduction of the nitro groupsafter imine formation may proceed via hydrogen transfer, using ahydrogenation catalyst such as Raney metals, e. g., Raney Ni and RaneyCo and platinum group catalysts, e. g., Pd/C and Pt/alumina.Hydrogenation may be conducted in the presence of hydrogen for reducingpartially remaining nitro and nitroso groups. Aromatization of thetetralin ring and reduction of the nitro group may be conducted in onestep. Specifically, the imine may be converted into a1,5-diaminonaphthalene derivative using a hydrogenation catalyst in thepresence of hydrogen.

Alternatively, a 5-nitro-1-tetralone derivative may be converted into a1,5-diaminonaphthalene derivative using a hydrogenation catalyst in thepresence of ammonia and/or an ammonium salt together with hydrogen.

All the reactions of imine formation, aromatization and reduction of thenitro group may be conducted in a gaseous or liquid phase, and batchwiseor in a continuous system.

A product 1,5-diaminonaphthalene derivative in the present invention isa compound represented by general formula (5), where R¹ to R⁴ and R⁶ toR⁷ are as defined in formulas (1) and (2).

Examples of a 1,5-diaminonaphthalene derivative used in the presentinvention include 1,5-diaminonaphthalene,2-methyl-1,5-diaminonaphthalene, 3-methyl-1,5-diaminonaphthalene,3-ethyl-1,5-diaminonaphthalene, 3-chloro-1,5-diaminonaphthalene,4-n-propyl-1,5-diaminonaphthalene, 6-isopropyl-1,5-diaminonaphthalene,6-n-butyl-1,5-diaminonaphthalene, 7-t-butyl-1,5-diaminonaphthalene,8-methyl-1,5-diaminonaphthalene, 6-chloro-1,5-diaminonaphthalene,2,6-dimethyl-1,5-diaminonaphthalene and4,8-dimethyl-1,5-diaminonaphthalene.

This invention will be further described with reference to, but notlimited to, Examples.

EXAMPLE 1 Preparation of a 4-(2-nitrobenzene)propane Derivative

In an ice-water bath was placed a 2 L (internal volume) four-neckedflask equipped with a reflux condenser, a thermometer, a dropping funneland a stirrer. In the flask were charged 50 g of 96% NaOH (1.2 mol) and64 g of water, and the mixture is dissolved. To the mixture was added1.2 L of 1,3-dimethyl-2-imidazolidinone (hereinafter, referred to asDMI), and the resulting mixture was stirred. To the mixture was addeddropwise a solution of 2-nitrotoluene (164.6 g, 1.2 mol) in DMI (360 mL)from the dropping funnel over about 1 hour. Then, to the mixture wasadded dropwise a solution of methyl acrylate (106.5 g, 1.2 mol) in DMI(360 mL) from the dropping funnel over about 3 hours while maintaining areaction temperature at 0 to 4° C. The reaction liquid was poured intoabout 5 L of ice-water. Then, sulfuric acid as a decomposition productof a superacid used in the subsequent step described in Example 2 waseffectively utilized for neutralizing the base. Specifically, themixture was neutralized to pH 5 to 7 with the residual sulfuric acidafter recovering by distillation FSO₃H used in cyclization of a4-(2-nitrobenzene) propane derivative at the end of the reaction. Then,the mixture was extracted with 300 mL of ethyl acetate, the extract wasdried over Na₂SO₄ and the residue was distilled at a reduced pressure(4×10⁻⁴ MPa) to give a viscous yellow liquid (160.6 g). Its purity asmethyl 4-(2-nitrobenzene)butyrate was 99% and an yield on the basis ofmethyl acrylate was 60%.

Then, a 4-(2-nitrobenzene)butyric acid may be prepared by treating theabove methyl ester as follows. In 200 mL of acetic acid was dissolved 55g of methyl 4-(2-nitrobenzene)butyrate (0.247 mol). To the mixture wereadded 44 g of water (2.47 mol) and 5 g of 3N aqueous HCl. The mixturewas heated for 5 hours under reflux for hydrolysis. After evaporatingacetic acid and water from the reaction mixture, the residue wasdissolved in 300 mL of ethyl acetate, and the organic layer was washedwith water three times. After drying over Na₂SO₄, ethyl acetate waspartially evaporated and the mixture was cooled to precipitate paleyellow crystals. After filtration and drying, 45 g of the product wasobtained as pale yellow crystals. Its purity as4-(2-nitrobenzene)butyric acid was 99.5%, and an yield on the basis ofthe ester was 87%.

EXAMPLE 2 Preparation of a 5-nitro-1-tetralone Derivative

Seventy five grams (75 g) of FSO₃H was placed in 300 mL (internalvolume) three-necked flask equipped with a reflux condenser, athermometer, a dropping funnel and a magnetic stirring bar. To thestirred mixture heated in an oil bath at 100° C. was added dropwise10.45 g of 4-(2-nitrobenzene)butyric acid from the dropping funnel over60 min for initiating cyclization to form 5-nitro-1-tetralone.

At the end of the reaction, the flask was equipped with a shortdistilling column, and then 65 g of FSO₃H was recovered by distillationat a reduced pressure (0.027 MPa). The recovered FSO₃H did not exhibitreduced activity in the cyclization even after repeated use in thereaction. Into 500 mL of ice-water was poured a mixture containing5-nitro-1-tetralone and sulfuric acid generated by decomposition of apart of the superacid, and the resulting mixture was extracted withbutyl acetate (150 mL×2). The extract was washed with water (100 mL×3)and dried over sodium sulfate. Butyl acetate was evaporated to givebrownish crystals containing 5-nitro-1-tetralone (9.0 g). A part of thecrystals was taken for quantification by GC. It was thus indicated thata conversion rate of 4-(2-nitrobenzene)butyric acid was 100% and thatthe desired 5-nitro-1-tetralone was obtained in an yield of 68% withoutdetecting isomers in which nitro and/or carbonyl groups were configuredin a different position.

The sulfuric-acid containing solution after phase separation of thereaction mixture using butyl acetate may be effectively utilized forneutralizing the aqueous solution containing the base used in Example 1.

EXAMPLE 3 Preparation of a 1,5-diaminonaphthalene Derivative

(1) Oxime Formation

In a 100 mL flask equipped with a reflux condenser were placed 2.26 g of5-nitro-1-tetralone and 60 mL of ethanol. To the mixture was added asolution of hydroxylamine hydrochloride (1.82 g) in water (4.5 mL). Thecontent of the flask was stirred with a stirring bar at reflux for 8hours. After evaporating the solvent, the residue was purified by columnchromatography (eluent: hexane/ethyl acetate=5/1)′ to give 2.2 g of5-nitro-1-tetralone oxime.

(2) Aminonaphthalene Formation

In a 100 mL flask equipped with a reflux condenser, an inlet tube forhydrogen chloride gas and a thermometer were placed 2.1 g of5-nitro-1-tetralone oxime and 40 mL of acetic acid. While bubblinghydrogen chloride gas, the mixture was heated at 100° C. for 4 hourswith stirring by a stirring bar. After allowing the mixture to be cooledto room temperature, a precipitated 5-nitro-1-aminonaphthalenehydrochloride was collected by filtration and rinsed with a small amountof acetic acid. After drying in vacuo, 5-nitro-1-aminonaphthalenehydrochloride (1.0 g) was obtained. No naphthalene derivativesisomerized in the amino or nitro group were detected.

(3) Reduction of a Nitro Group

To 5-nitro-1-aminonaphthalene hydrochloride were added water and ethylacetate. To the mixture was further added a 10% aqueous sodium hydroxideuntil the aqueous phase became pH 8. Then, the organic phase wasseparated and the aqueous phase was further extracted with ethyl acetatetwice. The combined organic phases were washed with an equal amount ofwater three times, dried over anhydrous magnesium sulfate and distilledoff the solvent, to give 5-nitro-1-aminonaphthalene as a red solid.

In a 50 mL flask equipped with a gas inlet tube and a thermometer wereplaced 12.5 mg of 5-nitro-1-aminonaphthalene, 12 mg of 5% Pd/C (50% wet)and 5 mL of DMF. The mixture was heated to 145° C. under nitrogenstream. When the temperature reached 145° C., the gas was replaced withhydrogen gas. While bubbling hydrogen, the mixture was stirred by astirring bar for 3 hours. After allowing the mixture to be cooled toroom temperature, the catalyst was filtered off. After adding 30 mL ofethyl acetate to the filtrate, the filtrate was washed with an equalvolume of water five times. The ethyl acetate solution was dried overanhydrous magnesium sulfate and distilled off the solvent. The residuewas purified by preparative TLC (eluent: hexane/ethyl acetate=1/1) to 10mg of 1,5-diaminonaphthalene as white crystals. No isomers in an aminogroup were detected.

EXAMPLE 4 Preparation of a 5-nitro-1-tetralone Derivative

Fifteen grams (15 g) of FSO₃H was placed in 100 mL (internal volume)three-necked flask equipped with a reflux condenser, a thermometer, adropping funnel and a magnetic stirring bar. To the stirred mixtureheated in an oil bath at 100° C. was added dropwise 1.902 g of4-(2-nitrobenzene)butanonitrile from the dropping funnel over 60 min.The reaction mixture was poured into 100 mL of ice-water, and themixture was extracted with ethyl acetate (50 mL×2). The combinedextracts were washed with water (50 mL×3), dried over sodium sulfate anddistilled off the ethyl acetate to give 1.8 g of 5-nitro-1-tetralone asbrownish crystals. A part of the crystals was taken for quantificationby GC, indicating that a conversion rate of4-(2-nitrobenzene)butanonitrile was 100% and that the desired5-nitro-1-tetralone was formed in an yield of 68%. No isomers havingnitro and/or carbonyl groups in different substitution positions weredetected.

EXAMPLE 5 Preparation of a 5-nitro-1-tetralone Derivative

A reaction was conducted as described in Example 4, except that 2.09 gof 4-(2-nitrobenzene)butyric acid was used as a starting material. As aresult, a conversion rate of 4-(2-nitrobenzene)butyric acid was 100%,the desired 5-nitro-1-tetralone was formed in an yield of 71%, and noisomers having nitro and/or carbonyl groups in different substitutionpositions were detected.

EXAMPLE 6 Preparation of a 5-nitro-1-tetralone Derivative

A reaction was conducted as described in Example 4, except that 2.23 gof methyl 4-(2-nitrobenzene)butyrate was used as a starting material. Asa result, a conversion rate of methyl 4-(2-nitrobenzene)butyrate was100%, the desired 5-nitro-1-tetralone was formed in an yield of 71%, andno isomers having nitro and/or carbonyl groups in different substitutionpositions were detected.

EXAMPLE 7 Preparation of a 5-nitro-1-tetralone Derivative

A reaction was conducted as described in Example 4, except that 2.09 gof 4-(2-nitrobenzene)butyric acid was used as a starting material and 15g of FSO₃H and 0.325 g of SbF₅ were used as a superacid. As a result, aconversion rate of 4-(2-nitrobenzene)butyric acid was 100%, the desired5-nitro-1-tetralone was formed in an yield of 81%, and no isomers havingnitro and/or carbonyl groups in different substitution positions weredetected.

EXAMPLE 8 Preparation of a 5-nitro-1-tetralone Derivative

Fifty grams (50 g) of 95% sulfuric acid was charged in a 100 mL(internal volume) three-necked flask equipped with a reflux condenser, athermometer, a dropping funnel and a stirrer. To the stirred mixtureheated in an oil bath at 100° C. was added 2.23 g of methyl4-(2-nitrobenzene)butyrate, and the reaction was continued for 8 hours.As a result, a conversion rate of methyl 4-(2-nitrobenzene)butyrate was100%, the desired 5-nitro-1-tetralone was formed in an yield of 58%, andno isomers having nitro and/or carbonyl groups in different substitutionpositions were detected.

EXAMPLE 9 Preparation of a 5-nitro-1-tetralone Derivative

A reaction was conducted as described in Example 8, except that 50 g ofpolyphosphoric acid was used as an acid and the reaction time was 6hours. As a result, a conversion rate of methyl4-(2-nitrobenzene)butyrate was 100%, the desired 5-nitro-1-tetralone wasformed in an yield of 56% and no isomers having nitro and/or carbonylgroups in different substitution positions were detected.

EXAMPLE 10 Preparation of 4-(2-nitrobenzene)butanonitrile

In an ice-water bath was placed a 2 L (internal volume) four-neckedflask equipped with a reflux condenser, a thermometer, a dropping funneland a stirrer. In the flask were charged 50 g of 96 wt % NaOH (1.2 mol)and 64 g of water, and the mixture was dissolved. To the mixture wasadded 1.2 L of 1,3-dimethyl-2-imidazolidinone (hereinafter, referred toas “DMI”), and the mixture was stirred. To the mixture was addeddropwise a solution of ortho-nitrotoluene (164.6 g, 1.2 mol) in DMI (360mL) from the dropping funnel over about 1 hour. To the mixture was thenadded dropwise a solution of acrylonitrile (31.8 g, 0.6 mol) in DMI (360mL) from the dropping funnel over about 3 hours while maintaining areaction temperature at 0 to 4° C. The reaction liquid was poured intoabout 5 L of ice-water, and the resulting mixture was neutralized with 3N aqueous HCl to pH 5 to 6. The mixture was extracted with 300 mL ofethyl acetate, and the extract was dried over Na₂SO₄ and distilled at areduced pressure (4×10⁻⁴ MPa) to give a yellow viscous liquid (63.4 g).Its purity as 4-(2-nitrobenzene)butanonitrile was 99% and an yield onthe basis of acrylonitrile was 55%.

EXAMPLE 11 Preparation of Methyl 4-(2-nitrobenzene)butyrate and4-(2-nitrobenzene)butyric Acid

A reaction and work-up were conducted as described in Example 10,replacing acrylonitrile with 106.5 g of methyl acrylate (1.2 mol) togive a yellow viscous liquid (161.5 g). The viscous liquid contained amixture of 4-(2-nitrobenzene)butyric acid and methyl4-(2-nitrobenzene)butyrate. They might be directly separated by columnchromatography or the ester alone might be collected by distillation.However, for minimizing a collection loss, the mixture was dissolved inethyl ether, and the carboxylic acid was esterified with diazomethaneinto the methyl ester, which was then distilled to isolate the methylester with a high purity. Its purity as methyl4-(2-nitrobenzene)butyrate was 99.5% and an yield on the basis of methylacrylate was 60%.

The carboxylic acid may be prepared by processing the methyl ester asfollows. In 200 mL of acetic acid was dissolved 55 g of methyl4-(2-nitrobenzene)butyrate (0.247 mol). To the mixture were added 44 gof water (2.47 mol) and 5 g of 3N aqueous HCl. The mixture was heatedfor 5 hours under reflux for hydrolysis. After distilled off acetic acidand water from the reaction mixture, the residue was dissolved in 300 mLof ethyl acetate, and the organic layer was washed with water threetimes. After drying over Na₂SO₄, ethyl acetate was partially distilledoff and the mixture was cooled to precipitate pale yellow crystals.After filtration and drying, 45 g of the product was obtained as paleyellow crystals. Its purity as 4-(2-nitrobenzene)butyric acid was 99.5%,and an yield on the basis of the ester was 87%.

EXAMPLE 12 Preparation of Methyl 4-(2-nitrobenzene)butyrate

In 1.2 L of DMI was added 31.6 g of 85 wt % powdered KOH (0.48 mol). Tothe stirred mixture was added dropwise 164.6 g of ortho-nitrotoluene(1.2 mol) and then 106.5 g of methyl acrylate (1.2 mol) over about 3hours while maintaining a reaction temperature at 0 to 4° C. Afterwork-up as described in Example 1, 115.2 g of a yellow viscous liquidwas obtained. Its purity as methyl 4-(2-nitrobenzene)butyrate was 99.5%,and an yield on the basis of methyl acrylate was 43%.

EXAMPLE 13 Preparation of Methyl 4-(2-nitrobenzene)butyrate

A reaction and work-up were conducted as described in Example 12, exceptthat the amount of 85 wt % powdered KOH was 7.9 g (0.12 mol) to give174.1 g of a yellow viscous liquid. Its purity as methyl4-(2-nitrobenzene)butyrate was 99.5%, and an yield on the basis ofmethyl acrylate was 65%.

COMPARATIVE EXAMPLE 1 Preparation of Methyl 4-(2-nitrobenzene)butyrate

A reaction and work-up were conducted as described in Example 12, exceptthat acrylonitrile and DMI were replaced with 106.5 g of methyl acrylate(1.2 mol) and 1.2 L of DMSO, respectively. After isolation, a purity asmethyl 4-(2-nitrobenzene)butyrate was 99.5%, and an yield on the basisof methyl acrylate was 3%.

EXAMPLE 14 Preparation of 4-(2-nitrobenzene)butyramide from4-(2-nitrobenzene)butyronitrile

In a 50 mL three-necked flask equipped with a reflux condenser and athermometer were placed 0.19 g of 4-(2-nitrobenzene)butyronitrile and1.96 of conc. sulfuric acid. With stirring using a stirring bar, themixture was heated at 100° C. for 3 hours. At the end of heating, thehot mixture was poured into 50 mL of ice-water, and the resultingmixture was extracted with ethyl acetate (20 mL×3). The organic phasewas sequentially washed with an equal volume of water, an equal volumeof saturated aqueous NaHCO₃ solution and an equal volume of water twice.After drying over anhydrous magnesium sulfate and distilled off theextraction solvent, the residue was purified by preparative TLC (eluent:ethyl acetate) to give 0.14 g of 4-(2-nitrobenzene)butyramide.

The analysis results are as follows.

¹H-NMR (CDCl₃): 7.90 ppm (1H, d-d, J=1.1 Hz, 8.1 Hz, Ar-H), 7.53 ppm(1H, m, Ar-H), 7.37 ppm (2H, m, Ar-H), 5.40 (2H, b-s, NH₂), 2.94 ppm(2H, d-d, J=7.6 Hz, 10 Hz, CH₂), 2.33 ppm (2H, t, J=7.4 Hz, CH₂), 2.03ppm (2H, m, CH₂);

IR (KBr): 3402, 3210, 1650, 1522, 1336 (cm⁻¹);

FD-MS: M/Z=209.

EXAMPLE 15 Preparation of a 5-nitro-1-tetralone Derivative

In a 10 mL flask equipped with a reflux condenser were charged 0.11 g of4-(2-nitrobenzene)butyramide and 1.5 g of fluorosulfonic acid. Withstirring using a stirring bar, the mixture was heated at 100° C. for 1hour. The reaction mixture was poured into 20 mL of ice-water, solidNaHCO₃ was added to the mixture until pH=8, and the mixture wasextracted with ethyl acetate (10 mL×3). After washing with water (30mL×2), the organic layer was dried over anhydrous magnesium sulfate anddistilled off the solvent. The residue was purified by preparative TLC(eluent: hexane/ethyl acetate=2/1) to give 0.02 g of5-nitro-1-tetralone. No isomers having a nitro group at a differentsubstitution position were formed.

(Effect of the Invention)

In a process where an ortho-alkylnitrobenzene derivative and a vinylcompound as starting materials are used to prepare a corresponding1,5-diaminonaphthalene derivative via a 5-nitro-1-tetralone derivative,the ortho-alkylnitrobenzene derivative and a vinyl compound having anelectron withdrawing group such as an acrylonitrile derivative and anacrylate may be reacted in the presence of a strong base to safely andcost-effectively provide an aromatic nitro compound such as anitrobenzenenitrile derivative, a nitrobenzenecarboxylate, anitrobenzenecarboxylic acid and a nitrobenzenecarboxamide. Furthermore,a 4-(2-nitrobenzene)butanonitrile derivative, a4-(2-nitrobenzene)butyric acid derivative, a 4-(2-nitrobenzene)butyrateor a 4-(2-nitrobenzene)butyramide derivative as a starting material maybe cyclized to provide a 5-nitro-1-tetralone derivative in a high yield.Furthermore, a 5-nitro-1-tetralone derivative may be used as a startingmaterial to provide a corresponding 1,5-diaminonaphthalene derivativewithout forming any isomer.

What is claimed is:
 1. A process for preparing a 1,5-diaminonaphthalenederivative comprising: (i) the first step comprising reacting anortho-alkylnitrobenzene represented by formula (1):

wherein R¹ to R⁴, which may be the same or different, representhydrogen, alkyl having 1 to 4 carbon atoms, aromatic hydrocarbon having6 to 12 carbon atoms, or halogen; and R⁵ represents hydrogen, with avinyl compound represented by formula (2):

wherein R⁶ and R⁷, which may be the same or different, representhydrogen, alkyl having 1 to 4 carbon atoms, or halogen; and X representsan electron withdrawing group, provided that R⁶ and R⁷ are mutually cis-or trans-configured, in the presence of a base, to produce an aromaticnitro compound represented by formula (3):

wherein R¹ to R⁷ are as defined in formulas (1) and (2); and Xrepresents an electron withdrawing group, which may be the same as ordifferent from X as defined in formula (2); (ii) the second step ofcyclizing the aromatic nitro compound represented by formula (3) toproduce a 5-nitro-1-tetralone derivative represented by formula (4):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2);and (iii) the third step comprising reacting the 5-nitro-1-tetralonederivative represented by formula (4) with an amine to provide anintermediate, which is then reduced and aromatized to produce the1,5-diaminonaphthalene derivative represented by formula (5):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2). 2.The process as claimed in claim 1, wherein X in formula (2) is oneselected from the group consisting of CN and CO₂R⁸ where R⁸ representsalkyl having 1 to 7 carbon atoms, cycloalkyl, aromatic hydrocarbonhaving 6 to 12 carbon atoms or aralkyl.
 3. The process as claimed inclaim 1, wherein X in formula (3) is one selected from the groupconsisting of CONH₂, CN, CO₂H and CO₂R⁸ where R⁸ represents alkyl having1 to 7 carbon atoms, cycloalkyl, aromatic hydrocarbon having 6 to 12carbon atoms or aralkyl.
 4. The process is claimed in claim 2, whereinthe reaction of the ortho-alkylnitrobenzene represented by formula (1)with the vinyl compound represented by formula (2) in the first step isconducted in the presence of at least one selected from the groupconsisting of a solvent capable of dissolving at least part of the baseand a catalyst capable of solubilizing the base.
 5. The process asclaimed in claim 4, wherein the solvent capable of dissolving at leastpart of the base is a cyclic urea derivative.
 6. The process as claimedin claim 5, wherein in the third step, a hydroxylamine derivative as theamine is reacted with the 5-nitro-1-tetralone derivative represented byformula (4) or an ammonia derivative as the amine is reacted with the5-nitro-1-tetralone derivative represented by formula (4) in thepresence of hydrogen peroxide, to provide an oxime represented byformula (6):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2),which is then converted by aromatization into a5-nitro-1-aminonaphthalene derivative represented by formula (7):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2),which is then reduced into the 1,5-diaminonaphthalene derivativerepresented by formula (5).
 7. The process as claimed in claim 5,wherein in the third step, an ammonia derivative as the amine is reactedwith the 5-nitro-1-tetralone derivative represented by formula (4) toprovide an imine represented by formula (8):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2),which is then reduced and aromatized to provide the1,5-diaminonaphthalene derivative represented by formula (5).
 8. Theprocess as claimed in claim 1, wherein the reaction of theortho-alkylnitrobenzene represented by formula (1) with the vinylcompound represented by formula (2) in the first step is conducted inthe presence of at least one selected from the group consisting of asolvent capable of dissolving at least part of the base and a catalystcapable of solubilizing the base.
 9. The process as claimed in claim 8,wherein the solvent capable of dissolving at least part of the base is acyclic urea derivative.
 10. The process as claimed in claim 4, whereinin the third step, a hydroxylamine derivative as the amine is reactedwith the 5-nitro-1-tetralone derivative represented by formula (4) or anammonia derivative as the amine is reacted with the 5-nitro-1-tetralonederivative represented by formula (4) in the presence of hydrogenperoxide, to provide an oxime represented by formula (6):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2),which is then converted by aromatization into a5-nitro-1-aminonaphthalene derivative represented by formula (7):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2),which is then reduced into the 1,5-diaminonaphthalene derivativerepresented by formula (5).
 11. The process as claimed in claim 3,wherein in the third step, a hydroxylamine derivative as the amine isreacted with the 5-nitro-1-tetralone derivative represented by formula(4) or an ammonia derivative as the amine is reacted with the5-nitro-1-tetralone derivative represented by formula (4) in thepresence of hydrogen peroxide, to provide an oxime represented byformula (6):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2),which is then converted by aromatization into a5-nitro-1-aminonaphthalene derivative represented by formula (7):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2),which is then reduced into the 1,5-diaminonaphthalene derivativerepresented by formula (5).
 12. The process as claimed in claim 2,wherein in the third step, a hydroxylamine derivative as the amine isreacted with the 5-nitro-1-tetralone derivative represented by formula(4) or an ammonia derivative as the amine is reacted with the5-nitro-1-tetralone derivative represented by formula (4) in thepresence of hydrogen peroxide, to provide an oxime represented byformula (6):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2),which is then converted by aromatization into a5-nitro-1-aminonaphthalene derivative represented by formula (7):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2),which is then reduced into the 1,5-diaminonaphthalene derivativerepresented by formula (5).
 13. The process as claimed in claim 1,wherein in the third step, a hydroxylamine derivative as the amine isreacted with the 5-nitro-1-tetralone derivative represented by formula(4) or an ammonia derivative as the amine is reacted with the5-nitro-1-tetralone derivative represented by formula (4) in thepresence of hydrogen peroxide, to provide an oxime represented byformula (6):

wherein R¹ to R⁴ and R⁶ to are as defined in formulas (1) and (2), whichis then converted by aromatization into a 5-nitro-1-aminonaphthalenederivative represented by formula (7):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2),which is then reduced into the 1,5-diaminonaphthalene derivativerepresented by formula (5).
 14. The process as claimed in claim 9,wherein in the third step, a hydroxylamine derivative as the amine isreacted with the 5-nitro-1-tetralone derivative represented by formula(4) or an ammonia derivative as the amine is reacted with the5-nitro-1-tetralone derivative represented by formula (4) in thepresence of hydrogen peroxide, to provide an oxime represented byformula (6):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2),which is then converted by aromatization into a5-nitro-1-aminonaphthalene derivative represented by formula (7):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2),which is then reduced into the 1,5-diaminonaphthalene derivativerepresented by formula (5).
 15. The process as claimed in claim 8,wherein in the step, a hydroxylamine derivative as the amine is reactedwith the 5-nitro-1-tetralone derivative represented by formula (4) or anammonia derivative as the amine is reacted with the 5-nitro-1-tetralonederivative represented by formula (4) in the presence of hydrogenperoxide, to provide an oxime represented by formula (6):

wherein R¹ to R⁴ and R⁶ to are as defined in formulas (1) and (2), whichis then converted by aromatization into a 5-nitro-1-aminonaphthalenederivative represented by formula (7):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2),which is then reduced into the 1,5-diaminonaphthalene derivativerepresented by formula (5).
 16. The process as claimed in claim 4,wherein in the third step, an ammonia derivative as the amine is reactedwith the 5-nitro-1-tetralone derivative represented by formula (4) toprovide an imine represented by formula (8):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2),which is then reduced and aromatized to provide the1,5-diaminonaphthalene derivative represented by formula (5). 17.(Previously added) The process as claimed in claim 3, wherein in thethird step, an ammonia derivative as the amine is reacted with the5-nitro-1-tetralone derivative represented by formula (4) to provide animine represented by formula (8):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2),which is then reduced and aromatized to provide the1,5-diaminonaphthalene derivative represented by formula (5).
 18. Theprocess as claimed in claim 2, wherein in the third step, an ammoniaderivative as the amine is reacted with the 5-nitro-1-tetralonederivative represented by formula (4) to provide an imine represented byformula (8):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2),which is then reduced and aromatized to provide the1,5-diaminonaphthalene derivative represented by formula (5).
 19. Theprocess as claimed in claim 1, wherein in the third step, an ammoniaderivative as the amine is reacted with the 5-nitro-1-tetralonederivative represented by formula (4) to provide an imine represented byformula (8):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2),which is then reduced and aromatized to provide the1,5-diaminonaphthalene derivative represented by formula (5).
 20. Theprocess as claimed in claim 9, wherein in the third step, an ammoniaderivative as the amine is reacted with the 5-nitro-1-tetralonederivative represented by formula (4) to provide an imine represented byformula (8):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2),which is then reduced and aromatized to provide the1,5-diamninonaphthalene derivative represented by formula (5).
 21. Theprocess as claimed in claim 8, wherein in the third step, an ammoniaderivative as the amine is reacted with the 5-nitro-1-tetralonederivative represented by formula (4) to provide an imine represented byformula (8):

wherein R¹ to R⁴ and R⁶ to R⁷ are as defined in formulas (1) and (2),which is then reduced and aromatized to provide the1,5-diaminonaphthalene derivative represented by formula (5).